Join container elements into a string

Sometimes, there is no algorithm in the library to accomplish a task at hand. We can use iterators, with the same techniques as the algorithms library, to easily write one.

For example, we often need to join elements from a container, with separators, into a string. One common solution is to use a simple for() loop:

for(auto v : c) cout << v << ', ';

The problem with this otherwise simple solution is that it leaves a trailing separator:

vector<string> greek{ "alpha", "beta", "gamma", 
                      "delta", "epsilon" };
for(auto v : greek) cout << v << ", ";
cout << '\n';

Output:

alpha, beta, gamma, delta, epsilon,

This may be fine in a testing environment, but in any production system, that trailing...